This description relates to a reference voltage supplying circuit and an analog to digital converter (ADC) equipped therewith. More particularly, the present invention relates to an ADC mounted with a reference voltage supplying circuit for supplying a stable minimum reference voltage and a maximum reference voltage to a pipeline ADC for converting an analog signal to a digital signal, and a reference voltage supplying circuit for converting an analog signal to a digital signal by the minimum reference voltage and the maximum reference voltage supplied by the reference voltage supplying circuit.
Concomitant with development of various flat display panels such as Plasma Display Panels (PDPs) and Liquid Crystal Displays (LCDs), markets for image display devices using flat display panels have made a sudden growth. Image signals which the image display devices can display on a screen using the flat display panels are varied. For example, the image display devices can receive various kinds of analog image signals including component signals of NTSC method, luminance and color signals, R, G, B signals and Y, PB, PR signals to display on a screen. The image display devices using flat display panels convert analog image signals to digital image signals and scale them to fit to the size of a screen in order to display a variety of analog image signals on the screen.
Furthermore, the processing speed of the ADC for converting the analog image signals to digital image signals should be heightened as the image display devices display the image signals of high resolution on the screen.
However, if the processing speed of the ADC is increased, there occurs a distortion of image signals, and the distortion of the image signals attenuates contrast and brightness of the images displayed on the screen. Accordingly, if the analog image signals are converted to the digital image signals, care should be taken into account that the image signals are not distorted even though the processing speed increases.
Pipeline ADCs are known for ADCs for converting analog image signals to digital image signals at a high speed without generating distortion to the image signals. The pipeline ADC is divided into a plurality of stages for converting analog signals to digital signals. Each stage is operated under the same timing, and results of each stage are turned over to next stage.
Consequently, the pipeline ADC is capable of converting the analog signals to the digital signals at a very high speed, and also capable of providing a wide variety of dynamic ranges relative to high frequency signals.
The pipeline ADC includes a plurality of flash ADCs and a plurality of MDACs (Multiplying Digital to Analog Converters). If reference voltages supplied to the plurality of flash ADCs and the plurality of MDACs are unstably varied, gain errors and offset errors occur to the digital signals converted from the analog signals. As a result, in designing a pipeline ADC, it is one of the most important elements to stabilize the reference voltage.